Services that can be supplied to end users over a data network can be categorized in Session-based services and Non-Session-based services. Generally, services belonging to the first category are those that enable a multimedia session (e.g., Audio and/or Video) to be provided by two network end points (software user agents) with the support of a signalling protocol towards a control plane, used for proper negotiation of the characteristics of the connection between the two end users and of the flows corresponding thereto. Services belonging to the second category are those that generally do not require a signalling protocol at the control level, such as peer-to-peer applications or applications linked to the distribution and use of multimedia contents and in general the services supplied in a client-server mode. It should be noted that also for Non-Session based services, a signalling protocol could exists between then two end points, but this signalling is confined to the Network Layer, without involving a Control Layer.
In the last few years the Session Initiation Protocol (SIP) has became established as the principal signalling protocol for Session-based services, and has also been selected by the 3rd Generation Partnership Project (3GPP) and by the Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN) in the construction of the architecture of the IP Multimedia Subsystem (IMS) in the Next Generation Networking (NGN).
The IMS is a standardised Next Generation Networking architecture for telecom operators able to provide mobile and fixed multimedia services. It uses a Voice-over-IP (VoIP) implementation based on a 3GPP standardised implementation of SIP, runs over the standard Internet Protocol (IP), and supports both packet-switched and circuit-switched existing phone systems.
With regard to the Session-based services, IMS will enable quality-guaranteed services to be supplied by network operators and service providers by controlling the network resources, with the possibility of carrying out corresponding charging. A further functionality provided by the IMS architecture is the so-called presence, which enables real-time user state information (e.g., present, occupied, not available, etc.) to be provided to applications that are enabled to request such information.
However, whilst the control of the Session-based services is easily implementable thanks to the SIP and to its interaction with the control plane, the majority (if not all) of the Non-Session-based services cannot rely on said interaction, and hence the control, also in relation to the multiplicity of the protocols involved in the Non-Session-based services, is considerably complex.
This problem has been tackled in TISPAN, a standardization body of ETSI, specializing in fixed networks and Internet convergence: Release 2 is in fact intended to support also Non-Session-based services, and hence to provide also in these scenarios all those functionalities available in the IMS framework, such as Presence, Resource Monitoring, Admission Control, Policy Control, and Accounting.
To this regard, it should be pointed out that the Non-Session-based services are today extremely heterogeneous. Specifically, Session-based services can include Voice over IP (VoIP)/Push to Talk, Buddy List, Click to Dial, Location-based info services, FMC (Fixed-Mobile Convergence & dual-mode telephony), while Non-session-based services can include IPTV (Internet Protocol Television), VoD (Video on Demand), video conferencing, Peer-to-Peer (P2P) Services, Gaming, VoIP, E-Mail/SMS/MMS, WEB Browsing, Data transfer (File Transfer Protocol (FTP), etc.).
In order to make the control layer application-aware also for the Non-Session-based services, it is necessary to make a considerable effort to improve the client-server “horizontal” model (i.e. a model that takes into account only of the signalling present at the Network Layer) typical of these services and characterized by heterogeneous protocols and technologies, with a mechanism that makes the control level aware of the service interactions.
The need to overcome the above-mentioned limits has led to the adoption of a network-based control framework, which entrusts at least in part the network with the task of intercepting the client-server horizontal communication flow during the use of a Non-session-based service and notifying particular events of interest of said activity to the control plane.
Based on this approach are the following patent applications: WO 2005/101782 A1 entitled “Method And System For Handling Content Delivery In Communication Networks”, which describes a network-based mechanism for controlling Unicast streaming, and WO 2007/073762 A1 entitled “Method And System For Managing Multicast Delivery Content In Communication Networks”, which describes a network-based mechanism for controlling Multicast streaming.
U.S. Pat. No. 6,052,730 addresses the problem of the network monitoring as regards the HTTP, proposing a solution that enables monitoring of, and active intervention on a browsing session, without requiring any reconfiguration of the client or interaction with the logs of the other servers and without requesting information from other servers (which cannot necessarily be controlled). The approach used is based upon re-direction of the requests to an intermediate server (proxy), that effects the desired tracing, and, by modifying the hyperlinks and the references to the pages sent by the web servers visited, leads the navigations of the browsing session to pass always through it.
In a similar way, the solution proposed in EP 1 619 853 describes a system that enters as a proxy into the Real Time Streaming Protocol (RTSP) traffic between a client and a server and that, instead of forwarding (some) RTSP messages from the client directly to the server (and vice versa) as a proxy would do, forwards them to an external module referred to as a Streaming Session Extension Module (SSEM), which manages state logic and enables notification to external applications of the state evolution. The SSEM module then re-forwards the message to the proxy module, after having possibly modified it based on the needs of the external applications. Finally, the proxy module sends the possibly modified message to the other end point (client or server).
Further, in the paper “Network Event Recognition”, Karthikeyan Bhargavan and Carl A. Gunter (March, 2004) there is described an approach for testing the network protocols, by capturing the communication flows, assembling them at a high level, and comparing (analysing) them with a finite-state machine that describes the standard for that given protocol. In practice, the method provides a language referred to as Network Event Recognition Language (NERL) that is able to describe the states and the events that generate the transition from one state to another, so as to supply information useful for evaluating the compliance of the implementation of a given protocol to the standard and for diagnosing the errors by attributing them to the application or to the network.
Along this line, in U.S. Pat. No. 6,741,595 a network processing system is described that is able to monitor the network traffic and capture and trace the IP communications that flow in the network. The system is able to scan the contents of the packets that traverse it, to associate said packets to sessions or flows, and to analyse them according to pre-determined criteria in order to replicate, save or re-direct towards another destination just the flows (or part thereof) that meet the adopted search criterion.
A solution based on the Deep Packet Inspection (DPI) is proposed in US 2006/0195556 to P-CUBE, which discloses a method and an apparatus for identifying and monitoring events and sequences of events in a Service Aware Network. In particular, this solution envisages:                definition, via software, of a first event that occurs in the network, and control of at least a portion of the network based on the first event;        definition, via software, of a matching operation that occurs in the network and that detects an occurrence corresponding to information transmitted over the network, and control of at least a portion of the network based on the matching operation;        definition of a concurrent operation, and control of at least a portion of the network based on the concurrent operation; and        re-synchronization in the absence of events, and corresponding control.        